VANCOUVER -- One of British Columbia's biggest motorcoach lines could grind to a halt this weekend.

Members of CAW Local 114 served 72-hour strike notice on Pacific Coach Lines yesterday, effective 12:01 a.m. on Saturday.

In late November, workers voted 91% in favour of striking. Their contract ended March 31 and talks since July have gone nowhere, said CAW national representative Gavin McGarrigle.

A mediated session at the Labour Relations Board is set for today in Vancouver.

"I'm not optimistic," said McGarrigle, who expected PCL to serve lockout notice yesterday afternoon.

"We hope to come to an agreement prior to any labour disruption," PCL sales and marketing director Darian Tooley said via e-mail.

"The spirit of bargaining continues as both parties would like to obtain a resolution as quickly as possible."

PCL carries 500,000 passengers a year and a service disruption would adversely impact scheduled travel and chartered services throughout Metro Vancouver, Whistler and Vancouver Island.

McGarrigle said the union wants a three-year deal with wage increases, but the company is offering a two-year contract with a signing bonus.

The 2006 collective bargaining agreement was reached amicably, he said.

"We're surprised we haven't been able to do that this time," McGarrigle said.

He said there are 127 unionized workers, 80 of whom are drivers earning $21 to $23 an hour.

The rest are ticket agents and mechanics.

McGarrigle claims PCL is using its non-union sister service Cantrail Coach Lines to cover overload on the Sea-to-Sky route. Cantrail normally runs from Vancouver to Seattle.